I was doing a POC around AVD in Gcc High and wanted to implement autoscale. Reading Microsoft’s documentation, the new autoscale is not in GCC High. I had to either write my own, use some 3rd party solution or leverage their original logic app/runbook solution. I opted using Microsoft’s original solution, but of course, it seems this is no longer being updated. It uses RunAs accounts which MS will retire on 9/30/2023.
I don’t understand why they just don’t update the solution to use a managed identity, but oh well. Not knowing if their new autoscale will make it to GCC High, I updated it to do a couple of things worth sharing.
The first thing we need to do is deploy the logicapp/automation account solution. It will deploy an automation account, upgrade some modules and deploy a logic app. We will want to make sure the system managed identity is enabled on the automation account and assigned the contributor role to the subscription. Opening up the runbook deployed, find
$AzAuth = Connect-AzAccount -ApplicationId $ConnectionAsset.ApplicationId -CertificateThumbprint $ConnectionAsset.CertificateThumbprint -TenantId $ConnectionAsset.TenantId -SubscriptionId $ConnectionAsset.SubscriptionId -EnvironmentName $EnvironmentName -ServicePrincipaland replace it with
$AzAuth = Connect-AzAccount -Identity add -EnvironmentName AzureUSGovernment if you are hitting GCC High.
I commented out $ConnectionAsset = Get-AutomationConnection -Name $ConnectionAssetName as we aren’t using a runas account anymore. In your logic app, you can just make the request parameter empty “ConnectionAssetName”: “”
At this point, we’re using a managed identity to log in. Great, but let’s start thinking why we are using this solution. Yes, we need more VMs to satisfy user load, but it is also a cost savings tool. If the VMs will shut down at night, why pay for Premium_LRS disks? We can easily add a function that converts the disk at shutdown and startup.
I added a simple function to the runbook:
function Set-AvdDisk {
param (
[string]$rgName,
$vm,
[ValidateSet("Standard_LRS", "Premium_LRS")]
[string]$diskSku
)
if ($convertDisks) {
if ($vm.PowerState -eq 'VM deallocated') {
write-output "VM $($vm.Name) is deallocated, checking disk sku"
$vmDisk = get-azdisk -ResourceGroupName $rgname -DiskName $vm.StorageProfile.OSDisk.Name
if ($vmDisk.sku.name -ne $diskSku) {
write-output "Changing disk sku to $diskSku on VM $($vm.Name)"
$vmDisk.sku = [microsoft.Azure.Management.Compute.Models.DiskSku]::new($diskSku)
$vmDisk | Update-AzDisk
}
}
}
}I just call that function in the foreach loop when the runbook starts a VM up:
That will ensure the disk is Premium sku when starting the VM up, but what about shutdown? That is the real cost saving. At the end of the script when all jobs are completed, I just run a simple powershell script that pulls back all the deallocated vm’s and runs the function above to convert the disks back to Standard_LRS.
Write-Log 'Convert all deallocated VMs disk to Standard Sku'
$stoppedVms = Get-AzVm -ResourceGroupName $ResourceGroupName -status | where {$_.PowerState -eq 'VM deallocated'}
foreach ($vm in $stoppedVms) {
Set-AvdDisk -rgName $vm.resourcegroupname -vm $vm -diskSku 'Standard_LRS'
}
When the runbook starts and a scale up or down action hits, you can see the result in the output of the job. The screenshot below is turning on a VM. It will change the disk sku back to Premium_LRS for that specific vm before starting it up.
Here is a screenshot of a VM being deallocated which you can see the disk being set to Standard_LRS to reduce cost.
Feel free to modify the script. I’ll honestly say that it took me 5 mins to put this together, so there is room for improvement, but this shows that the functionality will work. I’ll eventually get around to making this better, things like tag support to skip disks for some reason, but for now, enjoy.
Disclaimer: Test this before implementing.
https://github.com/jrudley/avd/blob/main/WVDAutoScaleRunbookARMBased.ps1
Azure Testing Site 